Generally, a Hot Runner System refers to a system for injecting melted resin into the inside of an injection mold under high pressure while maintaining the melted resin at high temperature on injecting the melted resin into the injection mold.
This hot runner system has been researched and developed constantly for reducing the wasted resin in manufacturing a plastic injection product. As is shown in FIGS. 1 and 2, the typical hot runner systems are implemented inside a mold in which a plurality of flat plates, i.e., a clamping plate 1, a space plate 2, a holding plate 3, and a cavity plate 4 in this order from the upper side are laminated.
A hot runner system 10 comprises a manifold 15 for dividing and supplying melted resin into several desired sites, a nozzle 20 fluidly connected to the manifold 15, and a cylinder 25 for injecting the melted resin by opening/closing the nozzle 20.
The manifold 15 is implemented inside the space plate 2 and maintains the melted resin supplied from an injection molding machine at high temperature by the heater (not shown).
Inside the manifold 15 are formed a plurality of resin traveling passages 16 like a grid type and a plurality of resin injecting holes 17 fluidly connected to the resin traveling passages 16.
The position in which the resin injecting hole 17 is formed on the manifold 15 depends on the volume and injection conditions etc., of the injection molding machine as implemented.
On the resin injecting hole 17 is firmly mounted a nozzle 20 for injecting the melted resin into the inside of the injection mold.
The nozzle 20 not only serves to keep the temperature of the melted resin so that the melted resin traveled through the manifold 15 is not solidified, but also serves to dispense the melted resin into the injection mold from the passage.
The distal end of the nozzle 20 is fixed to the surface of the mold, When the melted resin is dispensed through the nozzle 20, an amount by which the resin is dispensed into the mold is adjusted by raising/lowering actions of the piston 26 provided within the cylinder 25.
Then, the raising/lowering actions of the piston 26 are possibly performed by air pressure or fluid pressure supplied into the cylinder, and the amount of the dispensed resin from the nozzle 20 depends on for example the distance the piston travels.
However, the typical hot runner system 10 described above has a problem that a fracture on the nozzle 20 will be taken place in part or totally due to unbalance of force applied to the axial direction of the nozzle 20 and a bending stress applied to the nozzle 20 while the manifold 15 is thermally expanded on injecting melted resin into the mold, because an upper portion of the nozzle 20 is firmly fixed to the manifold 15 and a lower portion of the nozzle 20 is fixed to the surface of the mold to inject the melted resin into the inside of the mold using the typical hot runner system 10.
That is to say, there is a problem on the typical hot runner system that a split or fracture on the contact area will be taken place due to a bending stress applied to the nozzle 20 because the balance of force applied from a vertical direction of the nozzle 20 is changed into a horizontal direction of the nozzle 20 when the manifold 15 is thermally expanded by heating of the heater.